An instrument using alpha backscattering, alpha-proton nuclear reactions, and x-ray production by alpha particles and other auxiliary sources can be used on lunar landers to provide detailed analytical information concerning the lunar surface material. This information is important scientifically and can be the basis for utilizing efficiently lunar resources to build lunar colonies in the future. This alpha particle instrument uses radioactive isotopes, silicon detectors for the alpha and proton modes, and mercuric iodide detectors operating at room temperature for the x-ray mode. The alpha and proton modes of the instrument can provide an analysis for all elements (except hydrogen) present in amounts greater than about 1 percent by atom. These modes have excellent sensitivity and accuracy for the lighter elements, in particular, directly determining the amount of oxygen in the lunar soil. This is an element of paramount significance for the lunar resource mission. The x-ray mode makes possible a determination of Ti, Fe, and other important metals with even greater accuracy. In general, the x-ray mode provides increased sensitivity for heavier elements, in many cases achieving a sensitivity of several hundred ppm

Economou, T. E.

Turkevich, A. L.

English

NASA Technical Reports Server

20 New Technologies for Lunar Resource Assessment
Laser
20-50 J
10nsec
10
Tlme--of-FIlght
Mass
Spectrometer
1.5 cm
Fig. I.
200100
AMU
Fig. 3.
An experiment is now being set up (Fig. 5) to determine the
characteristics of such a laser mass spectrometer at long flight
distances. This experiment will determine the character of a future
flight instrument for lunar resource assessment. Such an instru-
Collision Mean Free Path
10 10
Pressure (Torr)
Fig. 4.
10
700 mj O-Swilcned
Nd:YAG Lasai
Fig. 5.
ment could determine the surface composition on a centimeter-
scale in one laser shot. Regions of high interest could be analyzed
with fine spatial resolution. Since the plasma also generates phot-
ons and neucra! particles, these could also be analyzed, providing
additional information. The laser-produced plasma will have suf-
ficient energy to create a shock wave in the lunar surface, which
could derive information on the lunar subsurface.
This instrument could provide substantial benefits to planetary
surface analysis, allowing smaller spatial resolution and faster anal-
ysis than other remote methods.
References: [ 1) Lubman D. M. (1990) Lasers and Mass Spec-
frosco/o1. Oxford Univ., New York. [2) Head J. W. (1988) NASA
Mars Con/. Proc., VoL 7), Am. Astron. Soc., 215-240.
AN a-p-x ANALYTICAL INSTRUMENT FOR LUNAR
RESOURCE INVESTIGATIONS. T. E. Economou and A. L.
Turkevich, Enrico Fermi Institute, University of Chicago, Chicago
IL 60637, USA.
An instrument using alpha backscattering, alpha-proton nuclear
reactions, and X-ray production by alpha particles and other
auxiliary sources can be used on lunar landers to provide detailed
https://ntrs.nasa.gov/search.jsp?R=19930008054 2020-03-24T07:24:42+00:00Z
LP1 Technical Report 92-06 21
analytical information concerning the lunar surface material. This
information is important scientifically and can be the basis for
utilizing efficiently lunar resources to build lunar colonies in the
future. This alpha particle instrument uses 'radioactive isotopes,
silicon detectors for the alpha and proton modes, and mercuric
iodide detectors operating at room temperature for the X-ray
mode.
The instrument is highly developed and has significant space
heritage. A similar instrument with alpha and proton modes was
aboard the Surveyor 5, 6, and 7 and provided the first chemical
analyses of the lunar surface in 1967-1968. During the 1970s,
it was considered for the Viking missions, and the instrument was
significantly miniaturized and its performance improved. An X-
ray mode was subsequently added to the alpha and proton modes
(a-p-x instrument [I]). Such an instrument was flown on the
Soviet missions Phobos 1 and 2 targeted for the mattian satellite
Phobos in 1988. Unfortunately, both spacecraft missions ended
prematurely before reaching Phobos.
Presently, the or-p-x instrument is on the payload of the Russian
Mars '94 mission that is scheduled to land on the surface of Mars
in 1995. This would provide a chemical analysis of the martian
surface much more detailed than that obtained by Viking. A similar
instrument is being developed for NASA as part of the straw-
TABLE 1. Expected accuracies (at 90% confidence limit) for
principal chemical elements.
, y , 1
Element Weight % Atom %
C ±0.2 ±0.4 .'•
O ±0.7 ±1.0
Na ±0.2 ±0.2
Mg ±0.8 ±0.7
Al ±0.4 ±0.3
Si ±1.2 ±0.9
K ±0.2 ±0.1
Ci ±0.2 ±0.1
Ti ±0.15 ±0.07
Fe ±0.4 ±0.2
TABLE 2. Examples of expected sensitivies for minor elements evaluated
for a basalt matrix using alpha and auxiliary sources.
Of 4- D + X-rav mndp*
Element
N
F
P
s
CIK'
V
Cr
Mn
Ni
Cu
Zn
Rb
Sr
y
Zr
Ba
La
Ce
Nd
Sm
Pb
Th
1 Iw
Sensitivity for
G,i.
Weight % Atom %
0.2
0.05
0.2
0.1
0.1
0.07
0.03
0.02
0.03
0.02
0.02
0.02
0.001
0.001
0.0005
0.0005
0.001
0.001
0.0008
0.0008
0.0005
0.005
0.005
0.005
0.3
0.06
0.14
0.07
0.06
0.04
0.013
0.008
0.012
0.008
0.007
0.007
0.0003
nnofn\-'.U\JV J
OflOOlw.vWI
0.0001
0.00017
0.00016
0.00013
0.00012
0.00007
0.0005
0.0005
A (VY^V-'.UVA.' j
K expected in the presence of a few weight percent of
man payload of the MESUR mission planned for Mars later in
this decade.
The alpha and proton modes of the instrument can provide
an analysis for all elements (except hydrogen) present in amounts
greater than about 1% by atom. These modes
sensitivity and accuracy for the lighter elements
directly determining the amount of oxygen irrthe
is an element of paramount significance for the
have excellent
, in particular,
lunar soil. This
lunar resource
ro
eo
SO
40-
3O
20
10
SURVEYOR X
APOLLO 11
SURVEYOR VI — SINUS MEOII
MARC
TRANQUILUTATIS
Ha Mq Ai Si "Co"
Fig. 1. A comparison between the results on samples of lunar mare on
Surveyor 5 and 6 with the data obtained later on Earth on samples brought
back by the Apollo 11 astronauts from a mare site. It is seen that the
Apollo data confirmed the Surveyor results to within the 90% error
estimates claimed 12].
Fe, and other important metals with even greater accuracy. In
general, the X-ray mode provides increased sensitivity for heavier
elements, in many cases achieving a sensitivity of several hundred
ppm.
The a-p-x instrument, due to its small size and low weight,
can easily be mounted on a mobile lunar vehicle (rover or mi-
crorover), an approach that is highly desirable during the first lunar
lander mission in order to increase the range of operations in the
search for suitable sites for a permanent lunar base. This in-
strument does not require the acquisition of a sample on board
the vehicle. It can be deployed to the lunar surface either directly
or mounted on an arm of the rover and then selectively placed
on samples of interest for analysis.
The entire instrument can be made to weigh less than 600 g
and to require less than 350 mW of power. It accumulates three
different energy spectra with ~I5 kbit per sample and therefore
imposes a very small burden on the spacecraft resources.
There are several areas where additional work is needed to
optimize the instrumenc for lunar-type missions. A very suitable
radioactive alpha source for the lunar missions is 242Cm. This
isotope has to be freshly prepared just before the mission. The
alternative, 24j4Cm, is more readily available, but would require
22 New Technologies /or Lunar Resource Assessment
longer times for sample analyses. Early tests with these sources
would be very desirable. Additional work with Hgl2 detectors and
their performance under lunar conditions (e.g., high temperatures)
will also have to be investigated.
References: [1J Economou T. E. and Turkevich A. L. (1976)
Nucl. Instr. Meth., 134. 391-400. |2J Franzgrote E.J. et al. (1970)
376-3
fflGH-RESOLUTION ELEMENTAL MAPPING OF THE
LUNAR SURFACE. Bradley C. Edwards, Frank Ameduri, Jef-
frey J. Bloch, William C. Priedhorsky, Diane Roussel-Dupre, and
Barham W. Smith, Los Alamos National Laboratory, Los Alamos
NM 87545, USA.
New instruments and missions are being proposed to study the
lunar surface as a result of the resurgence of interest in returning
to the Moon. One instrument recently proposed is similar in
concept ro the X-ray fluorescence detectors flown on Apollo, but
utilizes fluorescence from the L- and M-shells rather than the
K-shell. This soft X-Ray Fluorescence Imager (XRFI) will be the
topic of this presentation.
As was proven by the Apollo missions, the elemental com-
position of the lunar surface can be mapped using X-ray fluor-
escence from lunar orbit (1,21. However, the spatial resolution
and precision of the Apollo experiments were limited by both
exposure time and flux. Although future missions will have longer
lifetimes, the flux for K-shell fluorescence is still a primary limiting
factor and imaging keV radiation with a wide field of view is
difficult. However, the L- and M-shell fluorescence may provide
a solution because the much more intense solar radiation at less
than I keV will make the lower energy fluorescence flux up to
104 times more intense.
The theory behind the XRFI was discussed recently in Edwards
et al. 1 3] and indicates that the fluorescent emission should be
intense enough to be observed from lunar and even Earth orbit.
Preliminary concepts and designs have been worked out for an
XRFI that could be flown in lunar orbit in three years. XRFI is
one in the suite of instruments on the Lunar Resource Mapping
mission. The proposed instrument will provide maps with high
spatial resolution (1 km) of the surface distribution of a valuable
suite of elements (Al, Mg, Si, Ca, Na, Fe, Ti, etc.).
Although this design is not ideal for the lunar study, optimized
instruments with improved capabilities are only in the conceptual
stage and may not be feasible for many years.
The XRFI set of soft X-ray telescopes would fly in lunar orbit
to observe the fluorescent emission. The telescopes are of the same
design to be used on the ALEXIS mission with a normal incidence
multilayer mirror, a microchannel plate detector, and thin film
filtets. The technology, facilities, and software developed and
tested for ALEXIS are to be directly applied to the XRFI.
Each telescope would be tuned to an energy that corresponds
to an L- or M-shell fluorescent line. The intensity of each line
is proportional to the elemental abundance, surface structure, and
incident solar flux level. Details of the instrument, its require-
ments, specifications, and limitations will be presented.
Results from current feasibility studies of the XRFI concept
being done at Brookhaven will be discussed and presented along
with their implications. Future plans for studies, design, and con-
struction of the XRFI and the lunar community's involvement
is also a planned topic for this presentation.
Acknowledgments: We would like to thank D. Vaniman and
G. Heiken for helpful discussions concerning the lunar surface.
This work was completed under the auspices of DOE.
References: |l) Adler I. et al. (1972) Proc. LSC 3rd1, 2157-
2178. [2] Adler 1. et al. (1975) Space Science Instrumentation, I,
305-315, Reidel.[ 31 Edwards B.C. et al. (1991) GRL, 18, 2161-
2164. - -
N 9 3 - 1 7 2 4 5
Fig. 1. Diagram of current ALEXIS telescope design. A similar design
is to be used for the XRFI instrument on the LRM mission.
LUNAR AND ASTEROID COMPOSITION USING A
REMOTE SECONDARY ION MASS SPECTROMETER.
R. C. Elphic, H. O. Funsten, B. L. Barraclough, D. J. McComas,
and J. E. Nordholt, Space Plasma Physics Group, Los Alamos
National Laboratory, Los Alamos NM 87545, USA.
Laboratory experiments simulating solar wind sputtering of
lunar surface materials have shown that solar wind protons sputter
secondary ions in sufficient numbers to be measured from low-
altitude lunar orbit. Secondary ions of Na, Mg, Al.Si, K, Ca, Mn,
Ti, and Fe have been observed sputtered from sample simulants
of mare and highland soils [1 ]. While solar wind ions are hundreds
of times less efficient than those used in standard secondary ion
mass spectrometry, secondary ion fluxes expected at the Moon
under normal solar wind conditions range from —10 to >10* ions
cm"2 s"1, depending on species. These secondary ion fluxes depend
both on concentration in the soil and on probability of ionization;
yields of easily ionized elements such as K and Na are relatively
much greater than those for the more electronegative elements
and compounds. Once these ions leave the surface, they are subject
to acceleration by local electric and magnetic fields. For typical
solar wind conditions, secondary ions can be accelerated to an
orbital observing location. The same is true for atmospheric atoms
and molecules that are photoionized by solar EUV. Here we discuss
the instrumentation to detect, identify, and map secondary ions
sputtered from the lunar surface and photoions arising from the
tenuous atmosphere.
Solar Wind-sputtered Secondary Ions and Surface Compo-
sition: Our laboratory experiments subjected three simulants of
Apollo soil samples to ion bombatdment, and measured the relative
efficiencies of solar wind ions in sputtering secondary ions. The


An Alpha-p-x Analytical Instrument for Lunar Resource Investigations

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